Apparatuses for performing driving assist reflecting the driving characteristics of drivers are known. For example, Japanese Patent No. 4620001 discloses a driving assist apparatus that, before entrance of a curve, calculates the target curve entering speed from the curvature radius of the curve acquired from map information and a preset predetermined lateral acceleration, and automatically decelerates the vehicle speed to the target curve entering speed at the curve start point. In this apparatus, a threshold for determination on whether the vehicle speed reaches the target curve entering speed or not is changed according to the results from learning of the driving characteristics of the driver, and the changed threshold for determination is returned to the initial value at a timing according to the curve density (such as the number of curves existing within a predetermined distance) present ahead of the vehicle.
Moreover, Japanese Unexamined Patent Application Publication No. 2006-347531 discloses another apparatus for performing driving assist reflecting the driving characteristics of drivers. This driving assist apparatus learns the speed of a driver before entrance of a curve together with the curvature radius of the curve, and changes the target entering speed (target speed at a curve start point) preset for automatic control in a deceleration curve on a road approaching the curve from a reference value based on the results of the learning to automatically decelerate the vehicle speed.
Drivers brake in manners different from each other during driving on curve roads. The driving feeling of each driver during driving on curve roads significantly depends on the manner to decelerate until the vehicle reaches the curve start point, rather than the speed of the vehicle entering the curve start point. Accordingly, to appropriately reflect the preferences on the driving feeling of each driver in the operation of the driving assist apparatus, deceleration in the road approaching the curve before the curve start point should be focused.
Unfortunately, the objectives in driving assist of conventional drive assist apparatuses as described above are mainly to attain the target entering speed at the curve start point. In these apparatuses, the learned driving characteristics of drivers (namely, preferences of drivers) are only reflected in the threshold used in determination on whether the target entering speed coincides with the vehicle speed or in a correction amount of the target entering speed, and do not take into consideration the manners of deceleration in roads approaching curves which may affect the driving feelings of drivers.
In these conventional drive assist apparatuses, the timing and degree of deceleration in drive assist operations are automatically selected according to a variety of combinations of the target entering speed and the current vehicle speed to perform deceleration. For this reason, drivers do not know the timing when the automatic drive assist is started and how deceleration is performed, and may feel uncomfortable.
Accordingly, a driving assist apparatus is desired which can perform drive assist during driving on curve roads without giving uncomfortableness to drivers while appropriately reflecting the preferences of the drivers.